The present application is the U.S. national stage application of International Application PCT/NO00/00036, filed Feb. 3, 2000, which international application was published on Aug. 17, 2000 as International Publication WO 00/47106 in the English language. The International Application claims priority of Norwegian Patent Application 19990588, filed Feb. 9, 1999.
This invention relates to a device for use in eyesight testing, so-called eyesight-tests, which device constitutes a means of the kind used to test whether a person needs spectacles/contact lenses, and also to determine the degree of short-sightedness, long-sightedness etc., which device comprises a number of lenses varying in power (refractive power).
Conventionally, eyesight is tested by the use of a letter chart, the so-called Snellen""s chart, by which eyesight is measured in %.
Alternatively a standard spectacle case with loose spectacle lenses of different lens powers.
An automatic refractor of the type used by opticians, costs about NOK 100 000,-, a price level of a totally different order than that of eyesight testers of the kind that the present invention relates to. In this connection it may be mentioned that some people, including patients with reduced vision or visual defects of various kinds, often have an aversion to the use of large and bulky apparatus, such as autorefractors, and experience has shown that entirely satisfactory test results may be achieved for, for example, short-sightedness (myopia), long-sightedness (hypermetropia), and long-sightedness conditioned by old-age (presbyopia) by means of small, inexpensive aids, which may, through moderate modifications, also be employed in the testing of aberration of the cornea (astigmatism).
The object of the present invention has been to provide a device of structurally simple configuration, which is easy to operate by the user him/herself, while effectively contributing, at the same time, because of its particular configuration, to the achieving of sufficiently accurate measuring results by means for eyesight testing of the kind in question.
Said purpose is realized according to the invention, in that a device for eye-testing of the kind specified in the claims is additionally configured so that it exhibits the features that appear from the claims.
An eye-tester configured in accordance with the invention, comprises in its most general embodiment, a support and at least one, preferably two wheels supported rotationally in the support and carrying lenses embedded in the wheel or mounted therein, of different powers/refractive powers, which lenses are distributed along a circular path, said support comprising cover elements for receiving and supporting the lens wheel, said cover elements exhibiting an opening positioned on said circular path, which the lenses may be brought to correspond with, one by one.
At least two partially encased lens wheels are normally received in one support, each wheel being enclosed in essentially two parallel cover elements, the two pairs of cover elements preferably being hinged together, so that the support may be folded together to occupy half its area when the eyesight tester is not in use, while at the same time the eyesight tester will be less sensitive to external shocks, impact etc. in this folded, strengthened condition. The hinge axis may extend perpendicular to an imaginary connecting line between the two eye pieces/oculars.
Besides the eye piece/ocular positioned on the common circular path of the distribution pattern of the lenses, the centre of said path coinciding with the point of rotation of the wheel, at least one cover element of each pair may have at least one further, transverse hole, recess or similar slot/configuration leading into the adjacent side surface/circumferential portion of the wheel, more specifically so that it could correspond with one of a number of specifications of lens power corresponding to the refractive power of the lens located in the eye piece. These lens power specifications may be suitably spaced apart along an imaginary circle directly on the side surface of the respective rotary wheel, and appear one at a time in said through hole in one cover element, or they may be positioned individually on projections from the wheel circumference and appear in edge recesses, whereby the specification of lens power corresponds, at all times, with the overlapping lens(es) present in the ocular in each case.
Said recess may be formed in the circumferential region of the pair of covers as an edge recess which permitsxe2x80x94in addition to the task mentioned abovexe2x80x94direct access to the wheel circumference portion of the respective wheel, so that by one finger one may turn the lens wheel in the wanted direction, while one eye is preferably positioned in front of the eye piece of the respective half of the support.
Each one of a number of specifications of lens powers corresponding to the refractive power of the lens present in the ocular/eye piece in each case, may be carried by a projection extending from the respective wheel circumference, which projection passes, by rotation of the wheel, through a narrow slot between adjacent outer edges of opposed cover elements. This narrow slot extends over part of the circumferential extent of each support half.
When the eyesight tester support is provided with two lens wheels, one for the right eye and one for the left eye, the two support halves, each comprising a pair of cover elements and a lens wheel supported rotationally between them, will be mirror symmetric about the hinge axis.
By expansion of the eyesight tester according to the invention so that it comprises two wheels in each support half, whereby the possibilities of attachment will be increased so that it will be possible to test for aberration of the cornea (astigmatism), the circular paths on the two parallel wheels of each support half, along which lenses, differing from each other in power, are distributed, may be positioned either centrically or eccentrically in relation to each other. By eccentric positioning of these circular paths of distribution, it will be somewhat easier to separate the individual wheel at the circumference where they project through their respective recesses in the circumferential region of the pair of cover elements, in connection with the advancement of the respective wheel. In this embodiment, two individual lenses, one from each circular pattern of distribution, may be brought to correspond with one another within the eye piece of the respective support half. With the eye piece located on one circle of distribution of one set of lenses, the other should, relative to this eccentrically positioned circle, intersect the former within the eye piece.
To allow the same eyesight tester to be used by several persons who have different distances between the eyes, the two support halves with one eye piece/ocular each, are arranged independently rotational relative to the hinge. For this purpose each support half is formed, along its circumference and over a part thereof, with a groove open radially outwards and engaged by a peripheral projecting strip along the edges of the hinge connecting to the support halves. The groove and the projecting strip is formed mutually complementary, so that along the opposite connecting edges of the hinge, the projecting strip cannot be pulled out radially from the groove of the respective support half, which groove may be closed at its ends. The projecting strip may have a radially inner bulb, which engages the radially inner, widest part of the groove, which joins a narrower groove section ending radially at the circumference. The engagement of the projecting strips in the grooves along parts of the circumferential edges of the support halves, is conveniently subjected to friction on surface portions resting on each other, so that the set distance of the eye pieces is kept constant until another person is to have his/her eyesight tested with the same apparatus.
By two concentric/eccentric lens wheels in each support half, two holes may be formed in each half for indications of lens powers, one from each hole. One of these holes is located at a distance (radius) from the point of rotation of the associated wheel, different from the corresponding distance (radius) of the other hole. This special embodiment requires, moreover, that the wheels themselves be transparent or at least have transparent portions, so that the indications of lens power of the wheel at the back (relative the ocular/eye) are not covered, but can be seen through the wheel/wheel portion in front.